The present invention generally relates to telecommunications and more specifically to techniques for sending proprietary messages from a private Branch Exchange (PBX) over a packet-based network.
A private Branch Exchange (PBX) is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The PBX is owned and operated by the enterprise rather than a telephone company. PBX systems typically use a proprietary protocol to send signaling through local lines of a trunk. A trunk may include T1 and E1 lines.
Signaling using the proprietary protocol allows enhanced features to be carried in the PBX system. For example, four-digit calling, call transfer, call park, call pickup, displaying a caller name, and other supplemental features are sent over the PBX system as if it was in one office. Accordingly, remote offices, such as offices in different cities, may be connected as if they were one office. Advanced features are provided using the proprietary signaling; however, users are limited to using the PBX system with dedicated T1/E1 lines in order to use these features.
The proprietary protocol is typically a closed protocol that is only known by the manufacturer of the PBX system. Because outside telephone companies do not support carrying signaling for the PBX system over their networks, a dedicated circuit, such as a T1 or E1 line is used in the PBX system. These lines are typically very expensive. Also, full bandwidth is used regardless of whether a call is being switched on the lines. This is because the lines are dedicated to the enterprise and bandwidth is not allocated on demand.
Because of the closed nature of the proprietary protocol, outside devices cannot decode the proprietary signaling. If a system wants to send the call over a packet-based network (e.g., an IP network), the standard protocols, such as session initiation protocol (SIP), H.323, etc., do not support sending any proprietary information. These protocols only support sending standard information as defined by that protocol. Accordingly, the proprietary signaling that is sent in the PBX system cannot be sent using these packet-based/IP protocols. Thus, users are limited to using dedicated T1/E1 lines in order to transport information in the PBX system.
There is a solution called pseudo wire emulation (PWE) that allows T1/E1 lines to be carried on an IP network. However, this approach suffers from many problems. For example, the PWE approach transports all channels and even when only some of the voice channels are ideal. Also, PWE transports all voice channels in a much longer delay than a T1 and E1 line, which degrades the voice quality because no echo cancellation is provided by the PWE. PWE does not allow signaling using the proprietary protocol to be considered over the packet-based network. Rather, PWE is a point-to-point connection that does not switch or route the calls. The calls are transferred from a designated point to another designated point.
Accordingly, it is desirable to provide techniques for sending proprietary PBX signaling over a packet-based network.